Advances in phenol electropolymerization: from radical chemistry to functional films for sensors and energy storage

Electropolymerization provides a versatile one-step method for synthesizing adherent polyphenolic films directly onto conductive substrates. This process is fundamentally governed by the electrochemical generation of phenoxyl radicals and their subsequent coupling reactions to form networked polymeric films (with limited true cross-linking). The properties of these films—including their morphology, thickness, and electronic conductivity—are critically determined by synthesis parameters such as the monomer structure, electrode material, electrolyte composition, and applied potential. This review systematically examines the mechanism of phenol electropolymerization and the relationship between synthesis conditions and the resulting film characteristics. We then focus on the application of these tailored films in functional devices, highlighting their role as active elements in electrochemical sensors and as redox-active components in energy storage systems. Finally, we discuss the persistent challenge of electrode passivation and outline future research directions, including the development of hybrid composites and scalable synthesis protocols to advance the use of electropolymerized phenolic films in advanced technologies.